Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar: An electron paramagnetic resonance study with the spin trap DEPMPO

Electron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this study compared the respective roles of CS- and GPCS-derived free radicals on smoke-induced cytotoxicity and lipid peroxidation of filtered and unfiltered, machine-smoked experimental and reference cigarettes yielding a wide range of TPM yields. In buffer bubbled with CS the DEPMPO/superoxide spin adduct was the major detected nitroxide. Use of appropriate control experiments with nitric oxide radical (NO*) or carbonyl sulfide, and a computer analysis of spin adduct diastereoisomery showed that the hydroxyl radical (HO*) adduct of DEPMPO seen in GPCS-bubbled was rather related to metal-catalyzed nucleophilic synthesis than to direct HO* trapping. Unexpectedly a protective effect of TPM on murine 3T3 fibroblasts was observed in early (<3h) free radical-, GPCS-induced cell death, and carbon filtering decreased free radical formation, toxicity and lipid peroxidation in three cell lines (including human epithelial lung cells) challenged with GPCS. These results highlight an acute, free radical-dependent, harmful mechanism specific to the GPCS phase, possibly involving NO* chemistry, whose physical or chemical control may be of great interest with the aim of reducing the toxicity of smoke.

Regulation of cutaneous drug-metabolizing enzymes and cytoprotective gene expression by topical drugs in human skin in vivo

BACKGROUND

Individuality in the expression and regulation of hepatic drug-metabolizing enzymes (DMEs) and cytoprotective (CP) genes is an important determinant of treatment response. There is increasing evidence that many DMEs and CP genes are also expressed in human skin. Responses to topical drugs used to treat common skin diseases, such as psoriasis, are unpredictable and may potentially be rationalized, at least in part, by interindividual differences in cutaneous DME and CP gene expression.

OBJECTIVES

We investigated whether three topical drugs [coal tar, all-trans retinoic acid (atRA) and clobetasol 17-propionate] used in routine clinical practice modulated the expression of a variety of DME and CP genes [cytochrome P450s, glutathione S-transferases (GSTs) and drug transporters] in healthy human skin in vivo.

METHODS

Healthy adult volunteers (n = 30) were invited to participate in the study. Each subject was randomly allocated to receive two of the three study chemicals and one control site application. Crude coal tar (n = 13), atRA (n = 14) or clobetasol 17-propionate (n = 10) was applied under occlusion to photoprotected buttock skin for 96 h. A vehicle control (white soft paraffin) was also applied under the same conditions at an adjacent site in all subjects. Full-thickness punch biopsies (4-mm diameter) were then taken from treated and control sites. Total RNA was extracted and reverse transcribed into cDNA, which was used as a template in subsequent real-time polymerase chain reaction analysis, where fluorescent output was directly proportional to input cDNA concentration. Triplicate measurements of skin mRNA expression were made from each sample, and the arithmetic mean values taken. After logarithmic transformation, the paired t-test was used to compare values between treated and control skin.

RESULTS

Cytochrome P450s CYP1A1, CYP1A2, CYP1B1, CYP2C18, quinone reductase (NQO-1), GSTP1, gamma-glutamyl cysteine synthetase (gamma-GCS), glutathione peroxidase-1 (GPx-1), cyclooxygenase-2 (COX-2) and haem oxygenase-1 (HO-1) were induced by coal tar; CYP26, NADPH P450 reductase (CPR), GSTP1 and HO-1 by atRA; and CYP3A5 by clobetasol 17-propionate. In contrast, CYP1A1 and CYP1A2 expression was suppressed by atRA, and gamma-GCS and MRP1 by clobetasol 17-propionate. Marked interindividual variation in gene regulation by topical drugs was seen for the majority of genes examined.

CONCLUSIONS

These data demonstrate that topical drugs can modulate DME gene expression in human skin in vivo and indicate that variation in the expression and regulation of these genes may be a determinant of individuality in response to topical therapies for common skin diseases.

The topical treatment of psoriasis

According to the patients, improvement of efficacy, long-term safety and improvement of compliance are needed. The topical treatment has been innovated during the last decade. Most important are the introduction of two new classes of treatments: topical vitamin D(3) analogues and the retinoid tazarotene. To what extent, however, have we achieved developments which are in line with the needs as expressed by the patients? Improved efficacy has been realized by successful combinations of topical treatments. In particular, the combinations of dithranol, vitamin D(3) and tazarotene with a topical corticosteroid proved to be very effective with a reduced profile of side-effects. The efficacy of vitamin D(3) analogues and tazarotene is such that the efficacy of a potent corticosteroid (betamethasone-17-valerate) is approached; calcipotriol even showed an efficacy which is at least as good as this corticosteroid. The long-term safety of new compounds has been evaluated for at least 12 months in large studies. Remarkably for corticosteroids such information is available for only 12 weeks. However, intermittent applications of a topical corticosteroid in combination with another topical treatment provide an effective and safe long-term control of psoriasis. Compliance is a conditio sine qua non for an effective topical treatment. Important progress has been made to increase compliance. Short-contact dithranol has been popularized as an ambulatory treatment which is a highly effective approach as a care instruction programme. Formulations which are better from a cosmetical point of view have been developed for various topical treatments. Reduction of the frequency of applications proved to be possible for most treatments. Once daily applications for corticosteroids, vitamin D(3) analogues and retinoids have been developed, and intermittent applications, a few times per week, are possible for corticosteroids, which proved to be very effective with a reduced profile of side-effects, and are also developed for dithranol.

Coal tar: past, present and future

Crude coal tar has been used in the treatment of dermatoses for many decades. In the last few years its use has been limited to skin diseases such as psoriasis and chronic dermatitis. Newer topical modalities for psoriasis are being used increasingly for treatment, but have failed to replace crude coal tar as a first-line treatment of psoriasis. We review the pharmacology, chemistry and use of crude coal in order to reappraise its role as a therapeutic agent in dermatology.

Retinoic acid antagonizes basal as well as coal tar and glucocorticoid-induced cytochrome P4501A1 expression in human skin

Cytochrome P4501A1 is known to be expressed in skin and thus has been implicated in the pathogenesis of skin cancer due to certain environmental carcinogens. Retinoic acid (RA) has been used in chemoprevention of certain skin and other epithelial cancers. Therefore, we used Northern and Western analysis to determine the effect of externally applied RA on basal P4501A1 expression. RA reduced basal levels of P4501A1 mRNA and protein by 68 (n = 14, P = 0.005) and 75% (n = 7, P = 0.04) respectively. RA application also reduced basal levels of P4501A2 (another P4501A1 subfamily member) mRNA by 93% (n = 7, P = 0.001) as determined by reverse transcription-polymerase chain reaction. Interestingly, P4501A1 mRNA expression induced by coal tar or glucocorticoid (clobetasol) was reduced 46 (n = 10, P = 0.003) and 69% (n = 5, P < 0.05) respectively by RA co-application. Downregulation of basal P4501A1 expression and antagonism of coal tar mediated P4501A1 induction by RA may be a mechanism involved in chemo-prevention of skin and other epithelial cancer by RA.

Effects of topical preparations on the erythemogenicity of UVB: implications for psoriasis phototherapy

BACKGROUND

Topical preparations are sometimes applied before phototherapy without consideration of their potential to block UVB.

OBJECTIVE

Our purpose was to examine the ability of topical preparations to block UVB.

METHODS

Volunteers pretreated with mineral oil, a clear liquid emollient, 5% crude coal tar, 6% salicylic acid ointment, emollient creams, and petrolatum underwent minimal erythema dose testing. Transmission of UVB through a clear film coated with the preparations was measured.

RESULTS

Tars and salicylic acid blocked UVB. Thick application of petrolatum and emollient creams can reduce transmission of UVB. Mineral oil and a clear liquid emollient did not significantly affect transmission or erythemogenicity of UVB.

CONCLUSION

Clear liquid emollient and mineral oil can be used before phototherapy. If not removed before phototherapy, preparations containing tar or salicylic acid, or thickly applied petrolatum or emollients, can block UVB and presumably reduce its efficacy in the treatment of psoriasis.

The antifungal activity of a coal tar gel on Malassezia furfur in vitro

OBJECTIVE

Seborrhoeic dermatitis is associated with Malassezia furfur, but the exact role of this lipophilic yeast is still unclear. The in vitro antifungal activity of a coal tar gel, the base of the gel and coal tar (Stantar) itself has been evaluated against 54 different M. furfur strains, isolated from patients suffering from dandruff, seborrhoeic dermatitis and pityriasis versicolor.

METHODS

Minimum inhibitory concentrations (MICs) of the tested agents were measured by the agar dilution technique.

RESULTS

The coal tar gel was found to be able to inhibit growth of 52 out of 54 investigated M. furfur isolates in vitro at MIC values between 625 and 10,000 micrograms/ml-corresponding to 3-5 micrograms/ml coal tar. However, the gel base also appears to be a less potent inhibitor of in vitro growth of M. furfur. In addition, it could be demonstrated that coal tar alone has an antifungal potential on M. furfur in vitro. MIC values from 250 to 5,000 micrograms/ml for coal tar were found. Presumably, both coal tar as the active ingredient and the gel base contribute to the in vitro activity of the coal tar gel against M. furfur.

CONCLUSIONS

It is suggested that the effect of coal tar gel ointment in dandruff and seborrhoeic dermatitis therapy in vivo may be at least partly due to an antifungal activity of the coal tar but also of the gel base.

Carcinogens show comedogenic activity: a potential animal screen for tumorigenic substances

Formation of a comedo, an impaction of horny cells in sebaceous follicles, entails a metaplastic change in the differentiation patterns of the follicular epithelium. Since metaplasia is a requisite early stage in carcinogenesis, we postulated that carcinogens might be comedogenic. The rabbit ear was used to assay the comedogenic potentialities of an array of known tumorigens. Complete carcinogens and some tumor promotors were invariably strongly comedogenic at concentrations of 1.0% and below. Comedogenic chemicals commonly found in skin care products usually required concentrations of 40% and greater to induce comedones which were small in comparison to carcinogen induced comedones. We suggest that the rabbit ear model might be an easy and reliable way to screen for carcinogenicity.

In vitro comparison of antifungal effects of a coal tar gel and a ketoconazole gel on Malassezia furfur

Malassezia furfur seems to be a major pathogenetic factor in seborrhoeic dermatitis, a frequent human skin disease. To estimate the antifungal properties of a coal tar gel (5 mg ml-1 coal tar) which is used in the treatment of seborrhoeic dermatitis of the scalp, we compared its effects on the in vitro growth of M. furfur with those of a ketoconazole gel (20 mg ml-1 ketoconazole). None of the gels was fungicidal within incubation times up to 20 min. During a single application, both gels remain on the skin for only 5 min. Fungicidal effects are consequently unlikely to play a substantial therapeutic role. Fungistatic effects were observed with both gels. In cultures inoculated with 1 x 10(3) cells ml-1, a 1:49 152 dilution of the ketoconazole gel and a 1:768 dilution of the coal tar gel still showed inhibitory effects. At inoculum densities of 1 x 10(5) ml-1, both gels were fungistatic only in dilutions of a maximum of 1:40. Our results suggest that under clinical treatment conditions the fungistatic activities of both preparations should be comparable.

Pyridine and other coal tar constituents as inhibitors of potato polyphenol oxidase: a non-animal model for neurochemical studies

Potato polyphenol oxidase activity was strongly and noncompetitively inhibited by the "Perov mixture" of coal tar components and by pyridine alone, while phenol competitively inhibited the enzyme. These two inhibitors are structural components of the parkinsonogenic neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). By extension, dopamine and neuromelanin synthesis in the brain may be influenced by the inhibitory effects of such compounds upon the copper-dependent steps of tyrosine metabolism. The non-animal model used in this study may represent an alternative to the use of animal tissues in neurodegenerative disease research.

Detection of benzo[a]pyrene-diol-epoxide-DNA adducts in white blood cells of psoriatic patients treated with coal tar

An enzyme-linked immunosorbent assay (ELISA) was used to detect BPDE-DNA adducts in white blood cells of 23 psoriatic patients undergoing clinical coal tar therapy. Ten of these patients were reanalyzed 2-5 months after the end of the coal tar treatments. The results show that the mean adduct level during the treatment period was 0.26 +/- 0.16 fmole BPDE/micrograms DNA (7.7 +/- 4.9 adducts/10(8) nucleotides), while 2-5 months later the mean adduct level had decreased significantly (P less than 0.005) to 0.11 +/- 0.08 fmole BPDE/micrograms DNA (3.3 +/- 2.4 adducts/10(8) nucleotides). No relationship could be ascertained between the level of exposure and the amount of BPDE-DNA adducts. In addition, no difference in the level of DNA adducts was found between smoking and non-smoking patients.

Effect of UVB plus tar therapy on serum levels of interleukin-2 receptors in patients with psoriasis

Baseline serum levels of interleukin-2 receptor (IL2R) were measured in 65 patients with active psoriasis. IL2R levels in psoriatic patients were significantly higher than in healthy controls (582.4 +/- 289.23 u/ml vs. 369.64 +/- 111.10 u/ml; P less than 0.05), but did not differ statistically from values found in an atopic dermatitis control group (619.88 +/- 254.27 u/ml). Sex, age and severity of the disease do not affect levels of IL2R. The same IL2R levels were measured in 26 psoriatic patients receiving UVB plus tar therapy. This therapy, continued until clinical remission, lowered IL2R levels to values comparable to controls. This decrease may be due to an immunosuppressive effect of therapy.

[Cell kinetic effects of crude coal tar application plus long wave ultraviolet radiation on normal and hyperproliferative epidermis of guinea pig skin]

This study investigated the cell kinetic effects of combined treatment with crude coal tar and long wave ultraviolet (UVA) radiation on the normal and n-hexadecane-induced hyperproliferative epidermis of guinea pig skin. Flow cytometry was used to determine the proportion of cells in S phase (S fraction) and G2 + M phase (G2 + M fraction). Bromodeoxyuridine incorporation was used to determine the labeling index. Conventional histologic techniques were used to observe the mitotic index. In the normal epidermis after a single treatment with tar and UVA (1 J/cm2) or tar alone, the labeling index showed an initial decrease of 4 hr duration followed by moderate increase. The initial decrease was more pronounced in the tar-UVA-treated epidermis than in the tar-treated epidermis. The mitotic index was depressed during the first 12 hr. S- and G2 + M fraction showed no changes during the first 12 to 18 hour, and then increased in varying degrees. In the hyperproliferative epidermis after two applications of tar and UVA (1 and 4J/cm2) or tar alone, the labeling index was depressed during the first 12 hr, and mitotic index was below the control level until the 36 hr. The inhibitory effects on DNA synthesis and mitosis were more pronounced in the tar-UVA-treated epidermis than in the tar-treated epidermis. The S- and G2 + M fraction exceeded the control level in varying degrees during the whole experimental period. The results indicate that tar inhibits the epidermal DNA synthesis and mitosis by itself, and that the inhibitory effects of tar are intensified by the radiation of UVA.

[Antiproliferative activity of a highly purified coal tar preparation in comparison with clobetasol-17-propionate]

Coal tar and glucocorticosteroids are among the preparations used for the treatment of hyperproliferative inflammatory dermatosis. Coal tar generally seems to have a better effect on psoriasis capillitii than betamethasone-17-valerate. This finding is confirmed by investigations with human skin fibroblasts. The coal tar preparation Berniter has a strongly inhibitory effect on cell proliferation. The action of the preparation with tar can be clearly distinguished from the effect of the vehicle. At the ED50 concentration of the substance with tar, the vehicle without tar causes no inhibition. Based on weight equivalents Berniter has a greater inhibitory effect on proliferation of human skin fibroblasts than clobetasol-17-propionate. In the case of both substances protein biosynthesis is only affected at concentrations higher than those needed for the inhibition of proliferation. Berniter and the vehicle without tar have an equally strong effect on protein synthesis. Berniter affects the nucleoside triphosphatase bound to the nuclear membrane, and thus influences the nucleocytoplasmic transport of mRNA. The effect of the vehicle and the preparation containing tar on this parameter are very similar. Berniter has a positive effect on cell mobility. In preconfluent cultures the mobility of the cell is slightly increased and in confluent cultures significantly. Our results show that Berniter inhibits proliferation in cell cultures of human skin fibroblasts to a higher degree than clobetasol-17-propionate. It is to be assumed that neither the inhibition of protein synthesis nor the inhibition of mRNA transport play a causal role in the antiproliferative effect of coal tar. Inhibition of proliferation as a result of general damage to the cell can also be practically ruled out.

Monoclonal antibodies directed characterization of epidermal and hepatic cytochrome P-450 isozymes induced by skin application of therapeutic crude coal tar

A single application of crude coal tar (CCT) solution (USP) to the skin of neonatal rats was shown to induce epidermal and hepatic cytochrome P-450(P-450)-dependent monooxygenase activities. To further characterize the induction response, in this study we have utilized highly specific monoclonal antibodies (MoAb) 1-7-1, 2-66-3, and 1-98-1 directed against highly purified rat liver P-450s induced by 3-methyl-cholanthrene, phenobarbital and ethanol, respectively. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of hepatic microsomes prepared from CCT-treated animals showed a significant increase in the coomassie blue stainable proteins in the P-450 region; however, this was not evident in epidermal microsomes. Immunoblot analysis of epidermal and hepatic microsomes with MoAb 1-7-1 revealed strong immunoprecipitin bands in both tissues. MoAb 2-66-3 showed significant immunoreactivity only with hepatic microsomes. Interestingly, CCT treatment resulted in suppression of immunoreactivity with MoAb 1-98-1 in hepatic microsomes. MoAb 1-7-1 and 2-66-3 exhibited concentration-dependent inhibitory effects in aryl hydrocarbon hydroxylase and 7-ethoxycoumarin-O-deethylase activities induced by CCT application. MoAb 1-7-1 was substantially more effective in this respect. Epidermal and hepatic microsomes prepared from CCT-treated rats showed significantly greater metabolism of benzo(a)pyrene (BP). MoAb 1-7-1 and MoAb 2-66-3 inhibited BP metabolism in both the tissues. However, MoAb 1-7-1 was more inhibitory in this regard as compared to MoAb 2-66-3. These studies indicate that topical application of therapeutic CCT to the skin of neonatal rats results in induction of P-450 isozyme c in epidermis and isozymes b and c in liver, and that this induction is associated with the suppression of P-450 isozyme j in liver.

[Experimental and clinical demonstration of the antiproliferative effect of a highly purified coal tar fraction in a special gel vehicle]

In this study a combination of clinical and experimental investigations demonstrates the antiproliferative effect of the coal tar-containing preparation Berniter. From a concentration of 70 micrograms/ml onwards (= 0.35 micrograms coal tar/ml) Berniter inhibits DNA synthesis of transformed human keratinocytes in vitro. The growth inhibiting effect is reversible up to the ED50 concentration (257 micrograms Berniter/ml = 1.3 micrograms coal tar/ml). The tar-free vehicle has no identifiable effect on the proliferation of the cells at a concentration of 260 micrograms/ml. However, at higher concentrations (ED50 = 1023 micrograms/ml) the vehicle also inhibits cell growth, this inhibition being irreversible. The effect of Berniter and the tar-free vehicle on amino acid metabolism corresponds with the reduced growth rate. The ED50 concentrations (331 micrograms/ml for Berniter and 1445 micrograms/ml for the tar-free vehicle) are higher than those in the investigation of the proliferation. The clinical trial was performed in two groups of 12 and 11 patients, respectively, suffering from Psoriasis capillitii. After 3 days' topical treatment of both groups with salicylic acid for scaling, one group was treated for 4 weeks with betamethasone-17-valerate (in the following briefly called Bet-17-v), as a commercial lotion. The other group received Bet-17-v initially for 3 days and was then treated for 4 weeks with Berniter. The 4 parameters used for evaluation (erythema, scaling, infiltration and itching) showed a more significant improvement in the Berniter group than in the Bet-17-v group. Subjectively, treatment with Berniter was assessed to be preferable.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Hydroxypyrene as an indicator of the mutagenicity of coal tar after activation with human liver preparations

Liver S9 fractions were prepared from male Wistar rats, either non-induced or induced with Aroclor 1254 and from 5 human kidney transplant donors. The preparations were compared for their ability to metabolize the premutagens present in coal tar to mutagenic metabolites in the Salmonella mutagenicity assay towards strain TA98. Low levels of mutagenicity of coal tar were seen with human S9 preparations. The differences between the S9 mix of the 5 donors in capacity to activate premutagens were approximately 6-fold. The activation of coal tar by rat liver S9 preparations was higher than by the human S9 preparations. The metabolic conversion of pyrene in coal tar to 1-hydroxypyrene by the same human S9 preparations was determined in a parallel assay. 3 human preparations showed a high correlation between the formation of 1-hydroxypyrene and bioactivation of coal tar to mutagenic metabolites. The slope values of the individual regression lines were equal, suggesting that 1-hydroxypyrene is a good indicator for the activation of premutagens present in coal tar.

Induction of epidermal NAD(P)H:quinone reductase by chemical carcinogens: a possible mechanism for the detoxification

NAD(P)H:quinone reductase, which plays an important role in the detoxification of carcinogenic metabolites as well as oxidative cellular damage, was found to be present in epidermal cytosol where its specific activity far exceeds (140-160%) the corresponding hepatic value. The effect of topical application of crude coal tar, 3-methylcholanthrene and polychlorinated biphenyl Aroclor 1254, on epidermal and hepatic cytosolic NAD(P)H:quinone reductase activities was investigated in neonatal rats, Sencar and athymic nude mice. A single topical application of each agent resulted in significant increases in epidermal (185%-389%) and hepatic (150-255%) enzyme activities. This inducible enzyme may play an important role in the detoxification of reactive quinone species during the course of malignant neoplasia and against oxidative cellular damage in skin.

Human hair follicle benzo[a]pyrene and benzo[a]pyrene 7,8-diol metabolism: effect of exposure to a coal tar-containing shampoo

Assay systems for the evaluation of carcinogen interaction with human tissues are essential for assessing cancer risk. Hair follicles are a readily available source of human epithelial tissue and offer an excellent system with which to study carcinogen metabolism in human populations. In this study freshly plucked human hair follicles were employed to measure the metabolism of benzo[a]pyrene (BP), benzo[a]pyrene-7,8-diol (BP 7,8-diol), and the enzyme-mediated binding of [3H]-BP to DNA. The effect of human exposure to a crude coal tar (CCT)-containing shampoo, a preparation rich in polycyclic aromatic hydrocarbons (PAHs), on these parameters was also evaluated. Twelve healthy volunteers were studied before and after shampooing their hair daily for 4 days with the CCT-containing shampoo. Wide interindividual variation was observed in basal cytochrome P-450-dependent aryl hydrocarbon hydroxylase (AHH) activity which ranged from 0.6-17.6 fmol water-soluble BP metabolites/h/hair follicle (mean +/- SE of 32 individuals was 9.7 +/- 0.9). After use of the shampoo for 4 days AHH activity increased in 10 of the 12 volunteers (50-148%) and enhancement of enzyme-mediated binding of BP to DNA was detected in most subjects. Hair follicles were shown to convert BP to several metabolic species including BP 7,8-diol, a major precursor of the ultimate carcinogenic metabolite of BP. Benzo[a]pyrene-7,8-diol itself was also metabolized by the human hair follicles in this system. Clotrimazole, a known inhibitor of the metabolism of BP as well as the carcinogenicity of the hydrocarbon in rodent skin, was found to inhibit AHH and the in vitro metabolism of BP and BP 7,8-diol in human hair follicles. Oral administration of a similar antifungal imidazole, ketoconazole at a dose of 200 mg daily for 5 days, to healthy volunteers also resulted in greater than 90% inhibition of hair follicle AHH activity. These studies indicate that hair follicles represent an accessible tissue suitable for assessing the extent of PAH carcinogen metabolism in human subjects. Furthermore, enzyme activity critical to cancer induction by PAHs was shown to be inducible following the use of a CCT-containing shampoo. This carcinogen-activating enzyme system was substantially inhibited by imidazole compounds, suggesting that they may prove effective as anticarcinogens in human populations.

An investigation of the ability of antipsoriatic drugs to inhibit calmodulin activity: a possible mode of action of dithranol (anthralin)

Epidermal calmodulin (CaM) has been reported to be elevated in psoriasis and to decrease following clearance of psoriasis with treatment. We set out to investigate whether any of the principle drugs used in the treatment of psoriasis had inherent CaM antagonist activity. Utilizing a CaM-activated phosphodiesterase we have demonstrated that even at very high concentrations, the systemic drugs etretinate, methotrexate, and 8-methoxypsoralen, and the topical agents hydrocortisone and crude coal tar showed minimal CaM inhibitory activity. Dithranol (anthralin), however, whether freshly prepared or oxidized, produced substantial inhibition of CaM activity and was demonstrated to be a potent competitive antagonist of CaM, suggesting another possible therapeutic mode of action of dithranol in psoriasis.

Human epidermal blister: a convenient tissue for toxicological and genetic studies of benzo(a)pyrene metabolism

Benzo(a)pyrene (BP) metabolism has been studied in epidermal blisters maintained in a culture medium for 24 h and 48 h. The viability of the cells has been assayed by [3H]proline incorporation into proteins and by [14C]BP metabolism into unconjugated metabolites. A screen of BP metabolism in 19 individuals shows a great variation of basal epidermal activity. Induction of BP metabolism by the application of coal tar 24 h before the epidermal blister sampling, resulted in two- to eight-fold increase in BP metabolism. This induction is not increased when the coal tar application is repeated.

Biological monitoring of polycyclic aromatic hydrocarbons. Metabolites in urine

Assays of urinary mutagenicity, urinary 3-hydroxy-benzo(a)pyrene, and urinary 1-hydroxypyrene were used to study their suitability in estimating exposure to polycyclic aromatic hydrocarbons (PAH) in coal tar products. Rats exposed to coal tar solutions applied on the dorsal skin excreted mutagens, 3-hydroxy-benzo(a)pyrene, and 1-hydroxypyrene dose dependently in their urine. The correlation between the three parameters was high. Five dermatologic patients undergoing topical coal tar treatment excreted low concentrations of 3-hydroxy-benzo(a)pyrene and high concentrations of 1-hydroxypyrene. A significant correlation between the excretion of the two metabolites was found. The smoking workers of a coal tar distillation plant showed a significantly enhanced urinary mutagenicity compared with their nonsmoking colleagues, but an increase due to occupational exposure was not found. However, the concentration of 1-hydroxypyrene in the urine of these workers highly exceeded the upper 95 percentile of a reference population. The urinary excretion of 1-hydroxypyrene of smoking referents was not significantly increased compared with that of nonsmoking referents. The data suggest that urinary 1-hydroxypyrene is a sensitive and specific marker for the assessment of occupational exposure to PAH.

Altered patterns of cutaneous xenobiotic metabolism in UVB-induced squamous cell carcinoma in SKH-1 hairless mice

Cutaneous xenobiotic metabolizing enzymes including aryl hydrocarbon hydroxylase (AHH), 7-ethoxycoumarin O-deethylase (ECD), epoxide hydrolase (EH) and glutathione S-transferase (GST) activities were examined in SKH hairless mice chronically irradiated with UVB to induce squamous cell carcinoma (SCC). Enzyme activities in irradiated tumor-bearing skin were compared to those present in the skin of nonirradiated control animals as well as in unirradiated non-tumor bearing skin sites of the SCC-bearing mice. The inducibility of skin AHH and ECD in each set of animals was assessed following a single topical application of coal tar (1 ml/100 g). Enzyme-mediated binding of [3H]benzo(a)pyrene (BP) and its metabolite 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE-I) to epidermal DNA was also evaluated. Basal AHH and ECD activities in microsomes from UVB-irradiated SCC-bearing dorsal skin were 4.6- and 4.8-fold lower than those in dorsal skin of nonirradiated control animals. Enzyme activities in non-tumor bearing ventral skin from the UVB-irradiated SCC-bearing mice also were 2.2 to 2.8-fold lower as compared to activities in the nonirradiated control animals. The reduction in AHH activity paralleled the levels of enzyme-mediated binding of radiolabeled BP metabolites and of BPDE-I to epidermal DNA. GST activity was found to be increased (173%) in non-tumor bearing ventral skin of UVB-irradiated mice whereas no difference in activity between SCC-bearing dorsal skin and dorsal skin of control animals could be detected. EH activity was unchanged in each group of animals. Treatment with topically applied coal tar resulted in higher inducibility of AHH and ECD in both SCC-bearing (13-fold) as well as in non-tumor skin sites (6-fold) of UVB-irradiated mice than in skin of control animals (3-fold). Coal tar application also increased the covalent binding of [3H]BP and of the metabolite BPDE-I to skin DNA. This was greater in SCC-bearing dorsal skin (119-129%) than in nonirradiated skin of control animals (48-62%). Our studies suggest that the metabolism of BP by cutaneous cytochrome P-450 dependent monooxygenases is impaired in skin of mice irradiated chronically with UVB. The higher inducibility of these monooxygenases by topically applied coal tar and the enhancement of the associated enzyme-mediated covalent binding of BP metabolites and BPDE-I to epidermal DNA indicate that repetitive exposure of mammalian skin to UVB radiation can profoundly alter the activity and the inducibility of drug and carcinogen metabolizing enzymes.(ABSTRACT TRUNCATED AT 400 WORDS)

Isoquinoline is a possible anti-psoriatic agent in coal tar

Isoquinoline has been identified as a component of coal tar which causes interfollicular regions of parakeratotic stratum corneum in mouse tail epidermis to become orthokeratotic, with concomitant production of a granular layer. In this respect it behaves similarly to coal tar itself, and isoquinoline may contribute to the anti-psoriatic activity of coal tar.

Genetic monitoring of aluminum workers exposed to coal tar pitch volatiles

A group of 50 workers exposed to coal tar pitch volatiles (CTPV) in an aluminum reduction plant and a group of 50 non-exposed workers were selected to evaluate the genotoxic effects of CTPV exposure. A battery of tests was performed on 3 different body fluids; urine, blood and semen. Urine samples were evaluated for mutagenic constituents using the Ames/Salmonella assay. Cultured lymphocytes from blood samples were used to perform cytogenetic analysis. Semen samples were used to measure sperm count, percent abnormal sperm morphology and frequency of sperm carrying double fluorescent bodies (2-F). 14 of 28 (50%) exposed workers and 7 of 36 (19.4%) non-exposed workers had mutagenic urine. This difference was significant (p less than 0.01). Among the non-smokers a significantly higher percentage of workers who were exposed had positive urine (36%) compared to the non-exposed workers (5%) (p less than 0.05). Among the exposed group, more mechanics had mutagenic urine than did other types of workers. Overall chromosome aberration rates were similar in both exposed and non-exposed workers. Among exposed workers a significant inverse correlation (p less than 0.05) between age and chromatid aberration rate was observed. Results of semen analysis failed to detect differences between exposed and non-exposed workers. Results of these tests lend support to a battery approach to genetic monitoring and suggest a link between exposure to CTPV and genotoxic effects. Detection of exposure to mutagens at an early time offers an opportunity for disease prevention by the reduction of exposure.

Antibodies to orthokeratotic keratinocytes in monitoring the drug-induced inhibition of parakeratotic differentiation in adult and infant mice

Parakeratosis (PK) is a common feature of the abnormal epidermis in several disorders of keratinization. Tar phenols, retinoids and steroids which cause the inhibition of PK and the restoration of orthokeratosis (OK) are used for treating psoriasiform conditions. In this work, we studied two experimental models of the drug-induced inhibition of PK: (1) the suppression of the normal development of PK in the infant mouse tail and (2) the OK conversion of established PK in the adult tail. Two markers of OK were studied: the histological evaluation of the granular layer and the expression of cytoplasmic antigens linked to OK differentiation. It was demonstrated that high-boiling tar phenols cause a more potent inhibition of PK than betamethasone valerate. Most importantly, immunofluorescence showed that the switch to OK differentiation was located in the cells situated in a suprabasal position. The use of these immunological markers to investigate and anti-parakeratotic mechanisms has revealed that these drugs act at stages of keratinocyte differentiation which are distinct from those previously suggested.

Effect of crude coal tar in the mouse-tail model of psoriasis

A histological comparison was made between normal mouse tails and those treated with crude coal tar, and the effect of crude coal tar on the keratin profile of the living cells of treated animals was examined. The prophylactic effect of crude coal tar on the neonatal mouse tail is described. The variation in the anatomical site of prekeratin of the dorsal and tail epidermis of the mouse is reported. These results are discussed with reference to the use of the mouse tail as a model for screening drugs for the treatment of psoriasis.

Inducibility of arylhydrocarbon-hydroxylase activity in human hair follicles by topical application of liquor carbonis detergens (coal tar)

Arylhydrocarbon-hydroxylase (AHH) is a cytochrome P-450-dependent polysubstrate mono-oxygenase which plays an important role in converting some compounds (e.g. benzo[a]pyrene) to highly reactive carcinogenic species. A simple AHH assay is described, using [3H]benzo[a]-pyrene as substrate. 7,8-Benzoflavone (10(-4)M) inhibits 92% of the measured enzyme activity. Liquor carbonis detergens (which contains coal tar) induces AHH activity in human hair follicles in vivo. We suggest that using this simple assay, hair follicles would be a very suitable tissue to test whether the AHH-controlling gene is of significance in producing cancer.

[A study of the efficacy of disinfectants against anthrax spores]

The activity of disinfectants with regard to spores of Bacillus anthracis was determined in a suspension test. Creoline (10%) and also several other disinfectants for veterinary use showed no activity against spores of B. anthracis. Natriumdichloorisocyanuraat-dihydrate (2400 ppm active chlorine) and peracetic acid 0,25% demonstrated after 30 minutes of exposures at 20 degrees C in the presence of 4% horse serum a significant sporicidal effect. Under the same conditions formaldehyde 4% and glutaraldehyde 2% were also found to be sporicidal but only after 2 hours of exposure.

Animal assays for anti-psoriatic, retinoid and sun protective agents

It is possible to evaluate different dermatological therapeutic agents intended for human use in a variety of animal assays. This review will discuss some of these assays, and attempt to correlate animal and human skin responses. Psoriasis is a disease where changes in epidermal proliferation may be an important factor. It is possible to assay potential anti-psoriatic agents by measuring their ability to suppress DNA synthesis in the epidermis of hairless mice. This assay is predictive of the anti-psoriatic effectiveness of numerous agents including a variety of anti-proliferative drugs and anthralin, and has been used to evaluate the potential efficacy of purified coal tar shampoos and body preparations. The activity of the polyamine biosynthesis enzyme ornithine decarboxylase (ODC) is elevated in psoriatic skin, and it is induced in mouse epidermis by tape stripping. Retinoids can inhibit the induction of ODC activity, and this inhibition may be used to evaluate novel synthetic retinoids. Retinoids have beneficial effects on the abnormal keratinization found in various diseases. Rhino mice have multiple keratin-filled epidermal utricles, and the size of these is reduced by retinoid treatment. Observing the changes in the size of the utricles can be utilized to evaluate the effects of retinoids on keratinization. Sunscreen agents are tested on human volunteers by observing their ability to inhibit the erythema induced by exposure to solar-simulated light, to obtain a sun protection factor (SPF). It is possible to utilize the ability of sunscreens to inhibit other actinic-induced changes in the skin using animals. Parameters that may be measured include changes in DNA synthesis and ODC activity in the epidermis following ultraviolet irradiation. Some of these assays correlate well with human SPF determinations.

Effect of coal tar on cutaneous aryl hydrocarbon hydroxylase induction and anthralin irritancy

The inflammatory dose-response to topical anthralin and whole skin aryl hydrocarbon hydroxylase (AHH) activity were measured before and 24 h after application of a coal tar solution to the uninvolved skin of patients with psoriasis. The inflammatory response to anthralin decreased and total AHH activity increased after the tar treatment. A possible explanation is that anthralin or an irritant product is metabolized by AHH activity in the skin. Induction of AHH by coal tar increases its removal and reduces anthralin irritancy.

In vivo induction of aryl hydrocarbon hydroxylase in human scalp hair follicles by topical application of a commercial coal tar preparation

Five low-dose applications of a commercial coal tar preparation on a small scalp skin region resulted in an induction of aryl hydrocarbon hydroxylase (AHH) activity in freshly isolated human hair follicles. Large but reproducible interindividual differences in AHH-inducibility could be detected. The method offers the opportunity to measure AHH-inducibility, which has been correlated to the risk of developing chemical-induced cancer, in vivo in normal epithelium, a cell-type highly relevant for chemical carcinogenesis. Smoking habits did not have any effect on AHH-activity in freshly isolated hair follicles. Therefore the method potentially permits the identification of persons with high and low genetically determined AHH-inducibility.

Human skin aryl hydrocarbon hydroxylase

Aryl hydrocarbon hydroxylase (AHH) activity has been measured in full-thickness biopsies of human skin from patients with and without psoriasis. Basal levels of enzyme activity varied over a fivefold range and were not related to age, sex or clinical condition. Induction of AHH activity by the application of coal tar resulted in a two- to fivefold increase in activity above basal levels, which was not related to the presence or absence of psoriasis. Separation of human skin into dermis and epidermis showed that human skin AHH activity is predominantly dermal.

The role of active oxygen (1O2 and O(2)) induced by crude coal tar and its ingredients used in photochemotherapy of skin diseases

Crude coal tar (CCT) and certain photoreactive ingredients of CCT are photosensitizing agents used in the treatment of skin diseases (psoriasis, atopic eczema, etc.). Limited information is available in elucidating the mode of action of CCT in clearing psoriasis or causing skin photosensitization reactions. The production of singlet oxygen (1O2) and superoxide radicals (O(2) or HO2), the formation of interstrand cross-links (ICL) in DNA, and the skin photosensitization reaction caused by CCT or the ingredients present in tar preparations have been examined. Both type I (oxygen-independent) and type II (sensitized reactions requiring molecular oxygen) reactions are induced by CCT. Our data show that CCT and some of the photoreactive ingredients present in CCT produce 1O2, O(2), and ICL in DNA upon exposure to UVA radiation. Based on the equivalent concentration, the efficiency of various agents to produce 1O2 was of the following order: hematoporphyrin greater than phenanthridine greater than acridine greater than methylene blue greater than CCT greater than fluoranthrene greater than anthracene greater than pyrene greater than 8-methoxypsoralen greater than anthralin greater than chloroquine greater than anthralin dimer. The O(2) formation with CCT and its ingredients was also of the same order except for anthracene which was found to be a strong producer of O(2). The therapeutic effectiveness of CCT appears to be due to: (a) its cytotoxic effects, and (b) the production of 1O2, O(2), and ICL by CCT and its photoreactive ingredients. The skin photosensitizing (smarting, edema, and erythema responses) and carcinogenic properties of CCT may also be related to the production of 1O2 and O(2) and the formation of ICL which appear to be responsible for inducing the damage to the DNA and cell membrane.

The effect on epidermal DNA synthesis of a combination of topical steroid with either dithranol or tar as used for psoriasis

The hairless mouse was used to investigate the effects of a combination of glucocorticosteroid with either dithranol or tar on epidermal DNA synthesis, in order to determine whether such combinations reduce epidermal DNA synthesis more effectively than the single agents. Dithranol alone produced a significant local inhibition of DNA synthesis at concentrations of 0.1% and 0.05% but not at lower concentrations. Dose-response data for dilutions of clobetasol propionate and betamethasone 17-valerate showed progressive diminution of both local and systemic effects with decreasing concentrations. An additive effect was found from combining clobetasol propionate with dithranol and from combining betamethasone 17-valerate with liquor picis carbonis. These combined preparations were tested again after storage for 6 months and 2 months respectively and showed no loss of efficacy. These results lend justification to the use of these combined preparations in the treatment of psoriasis.

Fractionation, chemical analysis, and mutagenicity testing of low-Btu coal gasifier tar

A tar from a low-Btu coal gasifier was subjected to parallel fractionation, chemical analysis, and bacterial mutagenicity (Salmonella) assay. Like other coal-derived tars, it was a complex mixture containing some high-molecular-weight material and several classes of organic compounds as major constituents. The results of bacterial mutagenicity testing of fractions and subfractions of the tar suggest that neutral nitrogen-containing compounds, phenols, organic bases, polycyclic aromatic hydrocarbons, and some uncharacterized high-molecular-weight materials are mutagenic to Salmonella and therefore are potentially mutagenic in higher systems.

Lymphocyte sister chromatid exchange (SCE) frequencies in coke oven workers

Lymphocyte sister chromatid exchange (SCE) frequencies were determined for 12 long-term coke oven workers and 12 other age-matched steelworkers with no coke oven work exposure. All study participants were nonsmokers. The exposed group had a mean of 28.9 years' exposure to the coke oven emissions. SCE frequencies for the exposed individuals ranged from 7.97 to 11.20 SCEs per cell while the control individuals ranged from 6.73 to 10.60 SCEs per cell. The mean SCE frequency for the exposed group was 9.54 +/- SD 1.15 SCEs per cell, and was 14% higher than the 8.35 +/- SD 1.09 SCEs per cell of the control group (p = .016). The long-term exposure to coke oven emissions experienced by the coke oven workers may be the explanation for this small difference.

New coal tar extract and coal tar shampoos. Evaluation by epidermal cell DNA synthesis suppression assay

Coal tar therapy has been used for many years in the treatment of scaling skin diseases, including psoriasis and eczema. Previous studies of the potential effectiveness of tar have utilized phototoxic erythema assays with long-wave ultraviolet light (UV-A). However, in clinical use, coal tar is rarely used with UV-A, particularly for scalp disease. Therefore, we investigated a nonphototoxic approach to evaluate different coal tar products. Coal tar was found to suppress epidermal cell DNA synthesis in the hairless mouse model, and this is the basis for the assay presented. Using the epidermal cell DNA synthesis suppression assay, we observed that crude coal tar and a new extract of crude coal tar were equally effective and that a concentration gradient effect was achieved. In addition, four commercial coal tar shampoos assayed varied greatly in their ability to suppress epidermal cell DNA synthesis. One shampoo was washed after ten minutes and no significant alteration of suppressive effect was seen.

Evidence that coal tar is a mixed inducer of microsomal drug-metabolizing enzymes

Topical application of coal tar (U.S.P.) to neonatal rats resulted in the induction of hepatic cytosolic glutathione-S-transferase and microsomal epoxide hydrolase and aminopyrine N-demethylase activities. Analogous to the effect of the polychlorinated biphenyl Aroclor 1254, treatment of neonatal rats with coal tar resulted in a one nm shift to the blue region in the wavelength maximum of the hepatic microsomal hemoprotein cytochrome P-450. These results demonstrate that therapeutic coal tar contains both type I and type II inducers of hepatic drug-metabolizing enzymes.

Induction of neonatal rat skin and liver aryl hydrocarbon hydroxylase by coal tar and its constituents

Topical application of coal tar solution (USP) to neonatal rats resulted in the induction of skin and liver aryl hydrocarbon hydroxylase (AHH) activities. Furthermore indirect exposure of the animals to coal tar vapors resulted in induction of the enzyme in skin and liver. Cutaneous application of coal tar to pregnant rats resulted in induction of skin and liver AHH activity in both mothers and prenatal rats. Among several defined constituents of coal tar tested benzo(a)pyrene (BP), anthracene and acridine were found to have measurable induction effects on neonatal rat skin and liver AHH. These studies indicate that therapeutic coal tar solution as well as selected defined chemical constituents of coal tar are capable of altering the activity of AHH in skin and liver.

Antifungal activity of dermatological shampoos

The effect of several "medicated" shampoos on the growth of a variety of fungi was determined. Shampoos with as low as 0.5% coal tar were inhibitory to all strains, 2.5% selenium sulfide and 1 and 2% zinc pyrithione were significantly more inhibitory. Since these shampoos have substantivity for the human scalp, they may be useful as adjunctive therapy to griseofulvin in the treatment of scalp infections and minimize the risk of spread of viable spores to others in the environment.

The atrophogenic effect of crude coal tar on human epidermis

The effects of crude coal tar on human epidermis were studied in fourteen healthy young adult males. A 20% reduction in viable epidermal thickness, as determined by computer assisted analytical microscopy, was observed after 40 days of topical treatment. Prior to this long term effect of crude coal tar, an initial transient hyperplasia was observed during the first 2 weeks of treatment. These findings indicate that crude coal tar by itself can act as a cytostatic agent on normal human skin, when applied intensively.